Who Is WhatsApp’s Jan Koum?

In announcing Facebook’s deal to acquire the mobile-messaging app WhatsApp for $19 billion, Mark Zuckerberg said he’s “known Jan for a long time.” The rest of us, particularly people in the U.S., aren’t as familiar.

Jan Koum co-founded WhatsApp along with Brian Acton, a former colleague at Yahoo, and is the mobile-messaging company’s chief executive. He is taking on another big role: a Facebook board member.

But on his LinkedIn page, the 37-year-old Koum flies more under-the-radar. He lists himself as a QA tester and a senior tweet manager. If you want to know much more, he suggests, go see Brian’s profile. During his decade at Yahoo, he worked in infrastructure and security engineering. By his own admission in listing his education — barely graduating from MVHS in 1995 and dropping out of San Jose State University — he had other things on his mind.

Like its founder, WhatsApp is a quiet company. Sequoia says WhatsApp didn’t spend a single penny on marketing and is a veritable stranger in the U.S. — there is “no other home grown technology company that’s so widely loved overseas and so under appreciated at home,” the venture-capital firm said.

Not that WhatsApp didn’t toot its horn: Every two months the company announced its latest leap in monthly active users, usually to the tune of another 50 million. At last count, it had about 450 million active users.

In a December update, Koum said his company’s focus was on messaging and only messaging — no games, no advertising, no gimmicks. WhatsApp wants “to get out of the way. We want to let people have a conversation.”

In a Tumblr post on the deal Wednesday, WhatsApp investor Sequoia Capital talked about what shaped Koum’s focus on conversations: his experience emigrating to the U.S. as a 16-year-old and his desire to keep in touch with family back in Russia and Ukraine. (Forbes published a deep, deep profile Wednesday evening on Koum, his upbringing and how he built WhatsApp.)

Last May, Koum spent 30 minutes onstage at the D: Dive Into Mobile conference in New York. He talked through why the company was averse to advertising and selling the company (he said as much again months later), and why the app means so much to different people.